Infiltration cannula

ABSTRACT

An infiltration cannula and method of using the infiltration cannula during a tumescent infiltration procedure are disclosed herein. The infiltration cannula may have an outwardly flaring hub which may be wedged into an adit of a patient to minimize leakage of fluid being infiltrated into the patient. Also, the infiltration cannula may be utilized to hydrate a dehydrated patient by a medically untrained person. The infiltration cannula may also be used to deliver an antibiotic/vasoconstrictive drug solution to minimize surgical site infections.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part application of pendingU.S. Ser. No. 10/877,566, filed Jun. 21, 2004, which is acontinuation-in-part application of Applicant's prior U.S. Ser. No.10/442,370 filed May 21, 2003 entitled INFILTRATION CANNULA, and isrelated to pending U.S. patent application Ser. No. 10/877,337, filedJun. 25, 2004, the disclosures of which are expressly incorporatedherein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates in general to an infiltration cannulapermitting the infiltration of very large volumes of tumescent fluid ina safe and painless manner.

Definitions:

infiltration: an injection that causes a fluid to permeate or percolatethrough pores or interstices. Thus an infiltration refers to aninjection directly into tissue.

infusion: an injection that pours a fluid into a place or into (thelumen of a blood) vessel. Thus an infusion refers to an intravascularinjection.

injection: The action of forcing a fluid, etc. into tissue or cavity, asby means of a syringe, or by some impulsive force.

Tumescent Technique, Tumescent Infiltration: The tumescent technique isa method of subcutaneous drug delivery of large volumes of very dilutemedication together with dilute epinephrine in isotonic solution ofcrystalloid (e.g. physiologic saline, lactated Ringer's solution,Hartman's solution, etc) infiltrated directly into subcutaneous fat ormuscle or along the exterior length of a vein to produce swelling andfirmness, or tumescence, of the targeted tissues, and thus produce veryslow systemic absorption as a result of intense subcutaneousvasoconstriction, as well as direct hydrostatic compression ofcapillaries and veins.

Tumescent Drug Delivery, Tumescent Delivery: Tumescent drug delivery andsynonyms refer to the tumescent technique for delivering a drug into thesubcutaneous space. In other words, tumescent delivery is a process ofinfiltration of very large volumes of very dilute solutions oftherapeutic substances dissolved in a crystalloid solution intosubcutaneous tissue to the point of producing tumescence of the targetedtissue. Drugs other than lidocaine can be administered by means oftumescent delivery, that is, by subcutaneous infiltration of extremelydilute drug, with or without a vasoconstrictor such as epinephrine.

Tumescent Local Anesthesia (TLA) is local anesthesia produced by directinfiltration into subcutaneous tissue of large volumes of very dilutelidocaine (e.g., less than or equal to 1 gram/liter) and epinephrine(e.g., less than or equal to 1 milligram/liter) with sodium bicarbonate(e.g., 10 milliequivalents/liter) in a crystaloid solution such asphysiologic saline (NaCl) or lactated Ringer's solution. Although higherconcentrations can be used and still qualify as TLA, it is generallysafer to use the least (lowest) effective concentration.

Tumescent Local Anesthetic Solution (TLA Solution) is the localanesthetic solution used to produce TLA. Typically, a TLA Solutionconsists of a 10 to 20 fold dilution of commercially availableconcentration of lidocaine and epinephrine. Thus, a commercial solutionof lidocaine and epinephrine contains 10 grams of lidocaine per liter(10 gm/L) and 10 milligrams of epinephrine per liter. In contrast TLASolution typically contains very dilute lidocaine (<1 gram/liter) andepinephrine (≦1 milligram/liter) with sodium bicarbonate (10milliequivalents/liter) in a crystalloid solution such as physiologicsaline or lactated Ringer's solution. Typically the volume ofinfiltrated TLA Solution is so large that the skin and subcutaneoustissue becomes tumescent, in other words swollen and firm.

tumescent, tumescence: swollen and firm

tumescent liposuction: liposuction performed totally by local anesthesiausing tumescent local anesthesia.

tumescent fluid, tumescent solution: dilute solutions of therapeuticsubstances dissolved in a crystalloid solution intended for tumescentdelivery into subcutaneous tissue.

tumescent “drug”: the “drug” in the context as an ingredient in atumescent solution and its pharmacokinetic behavior as a result of thepharmacokinetics of a tumescent solution; for example tumescentlidocaine, tumescent epinephrine, tumescent antibiotic.

Tumescent Pharmacokinetics: The absorption pharmacokinetics (thepharmacologic and physiologic factors associated with the systemicabsorption of a drug) after tumescent infiltration of a drug isdramatically slower than the rate of systemic absorption of routineinjection of the drug. The intense vasoconstriction induced byepinephrine, slows the rate of drug absorption into the centralcirculation and prolongs the local effects of the drug. For example, theduration of routine local anesthesia with lidocaine is typically 2hours, in contrast the duration of local anesthesia with tumescent localanesthesia may be 12 to 18 hours or more. A similar prolonged effect oftumescent antibiotic infiltration significantly improves theprophylactic effect of preoperative antibiotic therapy in the preventionof surgical site infections.

adit: a small round hole in the skin (typically 1 mm, 1.5 mm or 2 mmdiameter) made by a skin-biopsy punch, and intended to be an access portfor percutaneous entry into the subcutaneous fat by a tumescentinfiltration cannula and/or a liposuction cannula.

Many medical procedures require infiltration of fluids, such as a localanesthetic. For example, liposuction may be performed entirely bytumescent local anesthesia which was invented by Jeffrey A. Klein. Dr.Klein first published the description of tumescent local anesthesia toperform liposuction in 1987 (Klein J A. The tumescent technique forliposuction surgery. J Am Acad Cosmetic Surg 4:263-267, 1987). Thetumescent technique was invented in order to eliminate the dangers ofliposuction surgery under general anesthesia and the associatedexcessive bleeding. With proper technique, tumescent infiltrationpermits liposuction totally by local anesthesia with virtually nosurgical blood loss.

One method of infiltration of local anesthetic is via a blunt tippedinfiltration cannula. Infiltrators are known as sprinkler-tip or Klein™(the present applicant) needle infiltrators. These cannulas areconstructed out of a rigid stainless steel and have one or moreapertures, which are typically round or oval, and are distributed aboutthe distal end of the cannula. The apertures are distributed over about15% to 25% or less than 5.0 cm. of the distal end of the cannula needle.These traditional infiltration cannulas are intended to be insertedthrough a small incision in the patient's skin and then moved in and outthrough the subcutaneous tissue while a dilute solution of localanesthetic (or other pharmaceutical solution) is ejected through thedistal apertures. Since the cannula needle is moved in and out, only thedistal end (e.g., about 15% to 25%) of the cannula needle may haveapertures. Otherwise, fluid may squirt out of the apertures and ontomedical professionals when the cannula needle is moved out too much.Such infiltrators typically have a blunt tip and require the placementof a small hole (made by a one mm skin-biopsy punch or a small surgicalblade) through which the blunt tipped cannula can be passed.Unfortunately, the piston-like in and out motion of the cannula causesthe patient discomfort.

Another type of infiltration cannula is the sharp tipped tumescentinfiltration cannula which is available as 1) a single long sharp needlesimilar to a spinal needle and 2) a group of short sharp hypodermicneedles each connected by separate plastic tube to a manifold thatdistributes TLA solution. The first type of needle is inserted intosubcutaneous fat and infiltration proceeds while the needle iscontinuously moved in and out along paths that radiate from the skinpuncture site. A targeted area is eventually anesthetized after multipleskin punctures. The second type, the group of short sharp needles,consists of a group of individual hypodermic needles each attached to anindividual IV extension tube, which are in turn connected to a multiport manifold which connected to a reservoir (IV bag) of tumescentfluid. These sharp-tipped tumescent infiltration devices have beenassociated with puncture-injury to deeper tissues such as the lungscausing pneumothorax or intra-abdominal viscera causing peritonitis.

In summary, there are two causes of pain associated with the blunt andsharp tipped infiltration cannulas. One significant cause of pain is acontinuous in and out motion of the cannula as it moves throughnon-anesthetized tissue. In order to deliver tumescent anestheticsolution throughout an entire compartment of subcutaneous fat, theanesthetist must move the cannula with a continuous to and froreciprocating motion, and repeatedly change directions. Each advance ofthe cannula through fat causes discomfort and pain. The second cause ofpain is associated with an excessively rapid distention of tissueresulting from a high rate of fluid injection into a relatively smallvolume of tissue via limited number of holes on the distal tip of theinfiltration cannula. Ironically, the pain associated with each of thesetwo factors often necessitates the use of narcotic analgesia, IVsedation, or general anesthesia in order to infiltrate local anesthesia.The present invention eliminates or greatly reduces these two sources ofpain.

Another method of fluid insertion is via a peripherally inserted centralcatheter, also called a PICC line comprising an elongate plastic tubethat is placed inside a vein of the patient. PICC lines are typicallyused for procedures requiring delivery of fluids over a prolonged periodof time. For example, a PICC line may be used when a patient needs toreceive intravenous (IV) fluids, such as medication or nutrients over aprolonged period of time, such as a week or more.

The On-Q® Pain Management System marketed by I-Flow® Corporation employsa flexible plastic or silicone catheter system for continuouslyproviding local anesthetic. This system provides prolonged localanesthesia by means of an elastomeric (elastic container) device thatcontinuously infiltrates a solution of local anesthesia over many hours.The On-Q® device comprises a long soft flexible tube with many smallholes arranged along a significant portion of the tube. The On-Q® deviceis designed to be initially positioned within a surgical wound at thetime of surgery. After the surgical wound is closed, the On-Q® devicepermits slow steady infiltration of a local anesthetic solution into thewound, thereby attenuating post-operative pain. The On-Q® device cannotbe inserted through a tiny hole in the skin into subcutaneous tissue.Therefore the On-Q device cannot achieve infiltration of localanesthesia and prevent post-operative pain in a preemptive fashion. Ithas been shown that preemptive local anesthesia in the form ofperipheral nerve blocks, can prevent nocioception by the central nervoussystem (CNS) during general anesthesia, and thereby prevent chronicpost-operative pain syndromes similar to “phantom-limb syndrome.” Thusthere is a need for a simple device that can permit the directpercutaneous insertion of a multi-holed infiltration cannula intosubcutaneous tissue for the localized delivery of medications such aslocal anesthetics, chemotherapeutic agents, or crystalloids forparenteral hydration.

Traditional techniques for subcutaneous injection of local anestheticsolutions (e.g. peripheral nerve blocks) use ahigh-concentration/low-volume of local anesthetic. This is associatedwith a rapid systemic absorption of the local anesthetic. In order toachieve a prolonged local anesthetic effect, the traditional techniquesfor using local anesthetics necessitate either frequent repeatedinjections or slow continuous subcutaneous infusion of the localanesthetic. As described above, repeated injections or piston-likemovement of the cannula causes patient discomfort. Slow continuousinfiltration may not be desirable in certain situations. Furthermore,continuous infiltrations restrict patient movement for extended periodsof time which also cause the patient discomfort. Thus, there is a needfor a system for infiltration of a local anesthetic into intactsubcutaneous tissue (not necessarily into peri-incisional tissue) whichdecreases patient discomfort pre-emptively, and allows prolonged localanesthesia either by rapid (less than 10 to 15 minutes) bolusinjections, extended infiltration (e.g. over intervals ranging from 15minutes to several hours) or continuous slow infiltration over manyhours to days. Furthermore there is a need for a devise that can providepre-emptive local anesthesia before a surgical wound is created. Thereis also a need for a percutaneously-insertable infiltration cannula,with applications that are unrelated to the delivery of localanesthesia, which can be easily inserted by rescuers with minimalclinical skill or training. One example is the need for a cannula thatpermits emergency fluid resuscitation in situations where an IV cannotbe established such as nighttime military combat conditions where usinga flash light to establish an IV access would be extremely dangerous.Another example is the need to provide emergency fluid resuscitation tolarge numbers of patients in acute epidemic diarrhea (dehydration)associated with biological warfare, or mass-trauma situations such as anatural disaster (earth quake) or terrorist attack. There is also a needfor a device that can easily provide localized fluid resuscitation toburn victims whereby fluid is infiltrated into the subcutaneous tissuedirectly subjacent to burned skin.

Other types of devices for delivering fluid to a patient exist in theprior art. For example, U.S. Pat. Pub. No. 2003/0009132 (Schwartz etal.) is directed to a micro-intravascular (never extra-vascular)catheter for infusing milliliter quantities of drugs for the lysis ofintravascular blood clots (i.e., a micro target). Another embodiment ofthe Schwartz device is intended to improve the precision and safety ofintra-myocardial delivery of micro-liter volumes of fluid for biologicgene therapy based angiogenesis.

Unfortunately, the Schwartz device requires a sterile high tech hospitalenvironment and demands fluoroscopy and ultrasound guidance. TheSchwartz device requires a highly trained, experienced and skilledmedical professional to operate. In particular, the Schwartzinfiltration catheter is defined by its obligatory guidewire andintravascular target. The intravascular insertion of the catheter viathe guidewire is a complex procedure that requires significant clinicaltraining, experience and skill Specifically, it involves 1) preparationwith a sterile surgical field, 2) making a skin incision and insertingan introducing catheter having coaxial stylet into the targeted vessel,3) removing the stylet, 4) inserting the guidewire through theintroducing catheter and into the vessel, 5) withdrawing the introducingcatheter from the vessel without disturbing the intravascular locationof the guidewire, 6) slipping the distal tip of the infiltrationcatheter over the proximal end of the guidewire, and advancing theinfiltration catheter over the considerable length of the guidewirethrough the skin and into the intraluminal space of the targeted vessel,7) withdrawing the guidewire and attaching the proximal end of theinfiltration catheter to a source of the therapeutic fluid to bedelivered into the targeted vessel. This insertion procedure is sospecialized that a majority of physicians do not have the requisiteexpertise to qualify for hospital privileges for inserting anintravascular catheter using a guidewire. Locating a clotted bloodvessel and inserting the Schwartz catheter into the vessel requires theultrasound guidance.

As understood, an important feature of the Schwartz device is the shape,size, direction and pattern of the holes on the infiltration cannula. Asstated in paragraph 15 of the Schwartz disclosure, “there is a need foran injection device that gives control over the concentration, pattern,and location of the deposition of an injectate.” The Schwartz device isintended to improve directional control over the direction of injectionof minute volumes of injectate.

The Schwartz device appears to be specifically designed to avoidvascular compression. For the small needle embodiment of Schwartz,vascular compression resulting from injecting excessive volume of druginto myocardium may precipitate infarction or arrhythmia Likewise, forthe long cannula embodiment of Schwartz vascular compression appears tobe contraindicated. The goal of infusing fluid into a vessel containinga blood clot is to open the vessel, and not compress it.

The Schwartz device also appears to be incapable of large volume (e.g.,multi liter) subcutaneous infiltration. The long plastic Schwartzcatheter appear to be specifically intended for intravascular use.Moreover, Schwartz cannula cannot have holes distributed along 100% ofits entire length based on a contention that such situation will lead toa contradictory situation. If the Schwartz device does have holes alongits entire length then either the entire length of the cannula wouldhave to be positioned inside a vessel (unlikely without attaching thecannula proximally to another catheter in which case the bulkyattachment mechanism would have to be passed through the wall of thevessel) or else some of the holes would have an extravascularlocation(unlikely because the therapeutic fluid would either leak ontothe patient's skin or extravasate into the perivascular and subcutaneoustissues). In either case, the potential for serious adverse effectswould be significant.

Moreover, the Schwartz device does not appear to be capable of beingreciprocated in and out of the subcutaneous tissue of the patient tolocally anesthetize an entire compartment.

In summary, the Schwartz infiltrator is intended for 1) intravascularinsertion which demands a complex guidewire procedure involving severalsteps, 2) intravascular drug delivery (for lysis of blood clots) orintra myocardial injections, 3) injection of a miniscule volume (microliters) of drug.

Another type of device for delivering fluid to a patient is described inU.S. Pat. No. 6,524,300, issued to Meglin. Similar to the Schwartzdevice, the Meglin device appears to be an intravascular device intendedto inject a “medical agent into the target lumen of the body.” (see Col.2, lns. 41-48). Meglin is specifically intended to be insertedintralumenally into “a lumen of a blood vessel or another cavity withina patient's body.” (see Col. 1, lns. 14-19). This is precisely oppositethe goal of a tumescent infiltration cannula. A tumescent infiltrationcannula is intended to deliver drugs to the subcutaneous space whichexcludes the vascular space and cavitary space. As such, the Meglindevice appears to be specifically designed to avoid vascular compressionand to not induce vasoconstriction. An important aspect of the Meglindevice appears to be the size and density of the apertures to controlthe rate of flow of fluidic medication. Moreover, it appears that themedical professional utilizing the Meglin device requires a great dealof training, expertise and education based on a contention that theinfusion segment of the device is located intravascularly by locating aradiopaque marker band with a fluoroscopy.

Another type of device for delivering fluid to a patient is described inU.S. Pat. No. 6,375,648, issued to Edelman, et al.. Similar to prior artblunt or sharp tipped infiltration cannulas, the apertures arerestricted to the distal 25% of the cannula. The reason is thatotherwise, the fluidic medication would squirt out of the apertures andcontaminate the operating room. Col. 2, lns. 22-25 states that “oncewithin the tissue of a patient a treatment solution may be infused intothe tissue by working the cannula 20 through the fat tissue of thepatient.” As understood, the Edelman device suffers from the samedeficiencies discussed above in relation to the blunt or sharp tippedinfiltration cannulas. The Edelman cannula is reciprocated in and out ofthe subcutaneous tissue, and thus, causes pain or discomfort to thepatient. Moreover, the only novel aspect of Edelman appears to be thecannula's Teflon coating.

Surgical site infections are a significant source of post-operativemorbidity and mortality. They account for 17% of all hospital acquiredinfections, require prolonged hospital stays and contributesubstantially to health care costs. The incidence of surgical siteinfection is a function of the type of surgical procedure, the surgeon,and the hospital. The risk of SSI is significantly associated with anumber of factors including anesthetic risk scores, wound class andduration of surgery.

The true incidence of SSI is probably higher than what has been reportedin the literature. The primary surgical team is often not aware ofincisional infections diagnosed after hospital discharge. Patients whohad SSI diagnosed after discharge require substantially more outpatientvisits, emergency visits, radiology services and home healthcareservices. A study published in 2004 found such infections cost $6,200per patient for home care expenses associated with wound care. The majorsources of infection are microorganisms on the patient's skin. A numberof preoperative skin care techniques have been used to limitconcentrations of bacteria at the surgical site, including antisepticpreparations, adhesive barrier drapes, topical antibiotics, hair removaland hand hygiene.

Antimicrobial prophylaxis with intravenous (IV) antibiotics is currentlythe most important clinical modality for preventing SSI. The consensusrecommendation for antimicrobial prophylaxis is for antimicrobial agentsto be given as an IV infusion of antibiotics to be given within thefirst 60 minutes before surgical incision and that prophylacticantimicrobial agents be discontinued within 24 hours of the end ofsurgery.

Recent Center for Disease Control (CDC) guidelines for antimicrobialprophylaxis do not mention preoperative perilesional infiltration ofantibiotics (http://www.cdc.gov/ncidod/dhqp/pdf/guidelines/SSI.pdf). Arecent review of surgical site infections only discussed intravenous(IV) delivery of prophylactic antibiotics. The possibility ofpreoperative peri-incisional infiltration to prevent SSI was notconsidered.

Several studies of SSI in the 1980's compared the effectiveness ofantimicrobial prophylaxis by IV infusion or by peri-incisionalinfiltration. A 1981 study of the incidence of wound infection among 405abdominal surgery patients found no significant difference between 1 gmof cephaloridine given intravenously or intra incisional at the end ofthe surgery. Following this trial, IV antibiotics at the induction ofanesthesia became standard practice.

An IV infusion of fluid is a common medical procedure to treat patients.Unfortunately, an IV infusion is associated with an inherent expense,difficulty and risk. There are also unfortunately times when an IV linecannot be established in the patient. By way of example and notlimitation, the patient may be burned such that a vein of the patientcannot be located to establish an IV access. The patient may have beentraumatized in such a way that will not allow a doctor to perform an IVcut down procedure. Additionally, the patient may be very obese suchthat the vein of the patient is difficult to locate. In othersituations, occurring in remote locations where a trained medicalprofessional is not available to establish the IV such as theinternational space station or on an airplane. Currently, there does notappear to be any in flight capability for treating an acute traumaticinjury on a plane or on the space shuttle. If the pilot or astronautsurvives the immediate effects of an explosion, burn, or decompressioninjury, or if there is an acute non-traumatic medical illness, it isassumed that the victim must return to terra firma for any significanttherapeutic intervention such as providing systemic fluid replacement.Other situations include a mass casualty situation where there areinsufficient number of trained medical professionals compared to thenumber of victims/patients, etc.

Other methods of delivering a drug to a patient other than an IVinfusion may be oral delivery of the drug. Unfortunately, oral deliveryof the drug results in inconsistent absorption of the drug into thegastrointestinal tract. The drug may alternatively be delivered viaperiodic intramuscular injections. Unfortunately, the fluidic drug serummay have varying levels of concentration at each of the periodicinjections.

BRIEF SUMMARY OF THE INVENTION

The present invention addresses the needs discussed above, identifiedbelow and those that are known in the art.

An infiltration cannula and method of using the infiltration cannuladuring an infiltration procedure is discussed herein. The infiltrationcannula preferably includes: a flexible cannula, a hub, and a rigidstylet. The flexible cannula has a proximal end and a distal end. Theflexible cannula also has a plurality of apertures disposed in a patternabout the distal end. The apertures are configured to infiltrate fluidinto the subcutaneous tissue of a patient. The hub is configured to beheld by a person performing the infiltration procedure. The hub has afirst end and an opposing second end. The first end is attached to theproximal end of the flexible cannula and the second end includes aconnector configured to connect to an input source for receiving thefluid to be infiltrated into the subcutaneous tissue of the patient. Thefluid flows from the connector, through the hub and into the flexiblecannula.

The flexile cannula may be manufactured of plastic and the rigid styletmay be fabricated from stainless metal or rigid plastic. The distal endof the cannula is closed to cover the tip of the rigid stylet or openwith a hole allowing the tip of the rigid stylet to protrude through.The tip of the rigid stylet is either sharp to directly insert throughthe skin of the patient, or so blunt that a skin incision is required topermit insertion of the rigid stylet and the cannula into thesubcutaneous space. The stylet may be formed to have either a solid orhollow cross-sectional configuration. The hollow rigid stylet may havesmall holes distributed along its length in a pattern dissimilar oridentical to the pattern of holes placed along the flexible cannula intowhich the stylet is inserted. Thus the stylet itself can be used as aninfiltration cannula.

The apertures may be arranged in a helical pattern or in a spiralpattern.

The apertures may be distributed over about 33% to about 100% of thedistal end of the tubular needle.

The apertures may be round or oval. The size of the apertures need notnecessarily be equal.

The fluid may comprise a local anesthetic or any other therapeuticsolution.

The infiltration procedure may be performed in conjunction withconventional medical procedures such as liposuction, but additionallymay simply be used as a mode of systemic drug delivery, or systemicfluid replacement therapy.

A method of infiltrating fluid into subcutaneous tissue of a patientusing an infiltration cannula, such as the one described above mayinclude the following steps.

A rigid stylet is inserted through a flexible infiltration cannula. Theinfiltration cannula is inserted through a patient's skin and into thesubcutaneous tissue or muscle tissue of the patient at a desired sitewith the stylet providing rigidity to the flexible cannula during theinsertion process. After the stylet is withdrawn from the cannula, afluid is provided from a fluid source via the connector. The fluid istransported from the connector through the hub and into the flexiblecannula. The fluid is ejected from the cannula into the subcutaneoustissue or muscle of the patient via the apertures.

The infiltration cannula used in performing the method preferablyincludes a connector for receiving the fluid from a fluid source, a hubin communication with the connector and a flexible cannula incommunication with the hub. The tubular needle has a plurality ofapertures disposed in a pattern about a distal end. The apertures areconfigured to infiltrate the fluid into the subcutaneous tissue ormuscle of the patient.

The above steps may be repeated intermittently, at intervals between afew minutes to many hours.

After the desired amount of fluid has been infiltrated at a given site,the infiltration cannula may be removed or may remain in place forpossible additional infiltration.

The infiltration cannula may additionally be inserted at a new site.

Multiple infiltration cannulas (e.g., two) may be used simultaneously.Use of multiple infiltration cannulas prevents disruption of theinfiltration process when one infiltration cannula is removed andrelocated. In particular, a second infiltration cannula may be insertedclosely adjacent to a first infiltration cannula which has partiallyanesthetized the area in which the second infiltration cannula is beinginserted to reduce the pain associated with inserting the secondinfiltration cannula into non anesthetized tissue. Multiple infiltratorscan be simultaneously inserted into separate areas to facilitate morerapid delivery of fluids.

The infiltration cannula discussed herein may provide for (1) a simplesubcutaneous insertion, (2) either regional drug delivery directly intosubcutaneous tissues or systemic drug when intravascular access is notpossible, and (3) infiltration of very large volumes (e.g., multiliters) of tumescent fluid. The infiltration cannula discussed hereinallows tumescent infiltration with less pain and greater safety.

In an aspect of the cannula, the same may be used to prevent or minimizesurgical site infections. For example, a solution of epinephrine, anantibiotic drug, and optionally, lidocaine may be administered to asurgical site.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other features of the present invention will becomemore apparent upon reference to the drawings wherein:

FIG. 1 is a side elevation view of a stainless steel infiltrationcannula with a closed tip shown inserted in subcutaneous tissue shown inpartial cross section;

FIG. 2 is a section view of the infiltration cannula shown in FIG. 1;

FIG. 3 is a side elevation view of a plastic infiltration cannula with aclosed tip shown inserted in subcutaneous tissue shown in partial crosssection;

FIG. 4 is an exploded view of the infiltration cannula shown in FIG. 3with a closed end;

FIG. 5 is a flow diagram illustrating an exemplary procedure for usingan infiltration cannula such as the one shown in FIG. 1 or the one shownin FIG. 3;

FIG. 6 is an exploded side elevation view of a plastic infiltrationcannula through which a stylet can be inserted with an open end; and

FIG. 7 is a side elevation view of a hollow sharp-tipped stylet withholes located along nearly the entire length of the stylet.

DETAILED DESCRIPTION OF THE INVENTION

As described in further detail below, the present invention takesadvantage of the tumescent technique in order to provide intermittent orcontinuous, brief or prolonged multi-liter infiltration of localanesthetic, physiologic fluid, antibiotics or other therapeutic solutionwith a significant decrease in patient discomfort due to the eliminationof the piston-like in and out motion of the cannula. Once the cannula ispositioned in place, there is no need to repeatedly move the cannula inand out through the tissue in order to deliver the fluid to a wide area.Using the tumescent technique and stainless steel versions of thepresent invention, the time needed in order to complete the infiltrationof a targeted anatomic area is reduced to nearly half of the timerequired when using traditional prior art cannulas. The device andmethod of the present invention can use multiple (e.g., two or more)infiltration cannulas simultaneously. While one cannula is activelydispersing tumescent fluid into the subcutaneous tissue, the surgeon canreposition a second infiltration cannula. This allows the infiltrationprocess to proceed without interruption, whereas prior art techniques ofinfiltration must be ceased each time the cannula is withdrawn from theskin and re-inserted into another direction.

The flexible plastic cannula version of the present invention provides ameans for relatively rapid fluid resuscitation in emergency situationssuch as when establishing an intravenous (IV) access is not feasible. Alarge volume of a tumescent crystalloid solution to treat intravascularfluid deficit may be delivered subcutaneously when an intravascular (IV)line cannot be started for fluid replacement. (e.g., remote area, obesepatient, burn/trauma victim, unavailable trained medical professional,etc.). As a further refinement, rapid systemic absorption of physiologicsaline can be achieved by adding a vasodilator drug to saline and usingthe tumescent technique to deliver the solution into subcutaneoustissue. For example, in the setting of overwhelming mass casualtieswhere there is no hope or expectation of trained clinical personnelbeing available, the ability of untrained first-responders to provideimmediate fluid resuscitation could save many lives. When a disastercauses an overwhelming number of trauma or burn victims, or when acholera epidemic leaves victims with life-threatening dysentery anddehydration, it is unlikely that there will be sufficient trainedpersonnel to start an IV line for IV fluid resuscitation. In such asetting, anyone (e.g., adult of average intelligence with minimalclinical training), perhaps even a victim himself, could simply insertone or more disposable plastic infiltration cannulas directly throughthe skin on the thigh(s) and into subcutaneous tissue and attach an IVbag and then allow the force of gravity to propel the fluid into thesubcutaneous space in a tumescent fashion. The resulting systemicabsorption and redistribution into the intracellular and intravascularcompartments could be life-saving. This emergency resuscitationprocedure relies on the combination of 1) the plastic-catheterembodiment and 2) absorption kinetics of tumescent fluid delivered tosubcutaneous tissue.

The flexible cannula may also have important applications as in treatinga wounded soldier in night-time combat conditions when establishing anIV access in total darkness is nearly impossible or using a flash lightmight attract enemy fire. The flexible cannula may similarly haveimportant applications in other areas of use such as treatingmass-casualty victims suffering hypovolemia as a result of epidemicinfections, biologic warfare, or trauma such as explosions, burns orradiation exposure. The flexible cannula similarly has applications insurgical patients wherein the surgeon can provide localizedpre-operative preemptive analgesia and simultaneously provide tumescentdelivery of a prophylactic dose of an antibiotic aimed precisely attissues targeted for surgical intervention.

As is well known, the tumescent technique was discovered by Jeffrey AlanKlein, M.D. (the present applicant) in 1985. Dr. Klein first published adescription of the tumescent technique in 1987 when he described the useof dilute lidocaine and epinephrine to permit liposuction totally bylocal anesthesia. The technique for tumescent local anesthesia is wellknown in dermatologic and plastic surgery literature. A detaileddescription of the tumescent technique has not been published inanesthesiology literature, and therefore, the unique benefits of thetumescent technique are not well recognized by anesthesiologists.

The tumescent technique comprises a drug delivery system that takesadvantage of a recently discovered reservoir effect of injecting arelatively large volume of relatively dilute solution of a drug into thesubcutaneous tissue.

The present invention takes advantage of the tumescent reservoirphenomenon for one of its important applications. After a large volume(e.g., multi liter) of fluid containing dilute epinephrine is injectedinto subcutaneous tissue, the epinephrine-induced vasoconstrictiondramatically slows the systemic absorption of the fluid and minimizessurgical blood loss. In effect, this large volume of subcutaneous fluidbehaves in a fashion that is analogous to the behavior of a slow-releasetablet in the stomach after oral ingestion. Although there is arelatively large total amount of drug in the patient's body, the drug isisolated from the systemic circulation by the fact that only the drug onthe outer boundary of the mass of drug is the available for absorption,whereas the portion of the drug located within the central portion ofthe mass of fluid is virtually isolated from the systemic circulation byvirtue of profound capillary vasoconstriction. In contrast, when thetumescent fluid does not contain epinephrine there is no clinicallysignificant vasoconstriction after tumescent infiltration, and thetumescent fluid is absorbed relatively rapidly. This has importantclinical applications in situations where patients are hypovolemic ordehydrated and unable to be given fluids by mouth or intravenously. Thetumescent technique permits rapid systemic hydration by directsubcutaneous or intramuscular injection of a large volume of fluidthrough a multi-fenestrated infiltration cannula described in thisinvention.

There is a prior art technique known as hypodermoclysis wherein a fluidis slowly and continuously infiltrated subcutaneously using a type ofsteel hypodermic needle, known as a butterfly needle, having a singledistal aperture in order to provide fluid to patients who cannot begiven fluids by mouth and for whom an IV access cannot be established.Typically hypodermoclysis is used in the treatment of infants, or cancerpatients, in which IV access is not easily achieved. The technique ofhypodermoclysis is typically used to deliver relatively small volumes offluid, for example an adult might receive 70 ml per hour. At this smallhourly volume hypodermoclysis is not an efficient method for the rapidsystemic delivery of fluid in emergency situations that might requiretwo to four liters per hour. The reason is that when using a cannulawith only a single distal aperture, the local interstitial fluidpressure increases rapidly immediately adjacent to the single apertureas fluid infiltrates locally, which in turn dramatically slows the rateof subsequent fluid flow into the area. In contrast, the multipleapertures formed along the length of the cannula as described in thepresent invention, distribute the fluid throughout a much larger volumetissue before there can be a sufficient increase in the interstitialfluid to decrease the rate of additional infiltration. Also, the amountof pain is reduced because the rate of fluid flow through each of theapertures is less than the rate of fluid flow through the singleaperture at the distal end. Further more, it is common practice toinfiltrate the tumescent fluid into the subcutaneous space underaugmented external pressure provided by an external peristaltic pumpspecifically designed for tumescent infiltration. By way of example andnot limitation, a preferred suitable peristaltic infiltration pump isdescribed in pending U.S. patent application Ser. No. 10/811,733, filedMar. 29, 2004, entitled INFILTRATION PUMP HAVING INSULATED ROLLERS ANDPROGRAMMABLE FOOT PEDAL, the disclosure of which is expresslyincorporated herein by reference.

The peristaltic pump provides a sufficient degree of pressure to easilyovercome the localized increased interstitial pressure associated withthe local effects of a tumescent infiltration. On the other hand, insituations where a peristaltic infiltration pump is not available, suchas in remote locations without any available electrical power, thepresent invention still permits relatively rapid tumescent infiltrationby virtue of the multiple holes distributed along the length of theflexible cannula. Furthermore, external hydrostatic pressure can beapplied to the fluid flowing into the flexible cannula from the fluidreservoir by means of gravitational force derived from elevating thereservoir one to two or more meters above the patient. When usinggravity to augment the flow of tumescent fluid, the infiltration processcan be continuous or intermittent. In exemplary embodiments, theintermittent injections are administered at intervals ranging from everyfew minutes to eight to twelve hours or more.

With the tumescent technique for local anesthesia, a large volume ofdilute solution of local anesthesia and epinephrine is injected into thesubcutaneous space resulting in a large bolus (or interstitialreservoir) of solution. The profound vasoconstrictive effect (shrinkingof the capillaries) caused by the dilute epinephrine, produces adramatic delay in the systemic absorption of the local anesthetic, whichprolongs the anesthetic effects of tumescent anesthesia for eight tosixteen times longer than traditional techniques.

Referring now to the drawings wherein the showings are for purposes ofillustrating preferred embodiments of the present invention only, andnot for purposes of limiting the same, FIGS. 1 and 2 illustrate astainless steel (reusable) infiltration cannula 10 and FIGS. 3-4 and 6illustrate a (single use) plastic infiltration cannula 30. The cannula10, 30 can be inserted under the skin 52 and into the subcutaneoustissue 50 and tumescent local anesthesia can be infiltrated eithercontinuously until the clinical goal is achieved or intermittently (byway of example and not limitation, once every eight to twelve hours).

Stainless steel infiltration cannulas 10, such as the one shown in FIGS.1 and 2, are formed having precision high quality and are preferablyreusable. These cannulas can be used to provide tumescent localanesthesia for surgical procedures, such as liposuction, which requiretumescent local anesthesia over a relatively large area.

The cannula 10 includes a tubular needle portion 12 which has a proximalend 14 and a distal end 16. The proximal end 14 of the tubular needle 12is attached to a hub 20 that is used by the anesthesiologist or surgeonto grasp and hold the cannula 10 during the infiltration procedure. Thehub 20 is connected to the tubular needle 12 at a first end 22 and has aconnector 24, such as a luer lock, at an opposing second end. Theconnector 24 is connected to a fluid source, such as tubing connected toan IV bag. Fluid enters the cannula 10 via the connector 24.

In exemplary embodiments, the tip at the distal end 16 is closed. Thelocal anesthetic is infiltrated into the patient via apertures 18located proximate the distal end 16 of the tubular needle 12 of thecannula 10. It is contemplated that the apertures 18, 38 and 54discussed herein may have a helical, spiral, linear or any random orordered pattern. Also, in exemplary embodiments, the apertures 18 aredisposed along the distal end 16 of the cannula 10 in a spiral orhelical pattern and are distributed over the distal 33% to 100% of thetubular needle 12 of the cannula 10. For example, if the length of thetubular needle D is 15 cm and the apertures 18 at the distal end 16cover a length d1 of 5 cm, the pattern of apertures of the cannula 10are preferably distributed over 33% of the tubular needle 12 of thecannula 10. The size of the aperture and density of apertures on thetubular needle is limited by the structural integrity of the cannula. Ifthe apertures 18 are too large or too close together then the cannulamay bend or break during use (e.g., routine clinical applications).Prior art cannulas wherein the apertures are limited to the distal 25%of the cannula eject the fluid into the subcutaneous tissue at a highrate so as to cause discomfort to the patient. The apertures 18 whichare located along a greater length of the cannula compared to prior artcannula allows fluid to flow out of each of the apertures at a slowerrate but to achieve a greater amount of fluid flow as an aggregate so asto reduce the amount of discomfort to the patient due to the rate atwhich fluid flows out of each of the apertures. When tumescent fluid isinjected into subcutaneous tissue, tumescent fluid spreads by means ofsimple bulk-flow through the interstitial gel substance. This process isextremely rapid and unimpeded by fibrous tissue.

The proximal portion 14 of the cannula 10 may be devoid of apertures inorder to prevent fluid from leaking out of the cannula insertion site inthe skin. Alternatively, if the proximal portion 14 of the cannula hasaperture(s), then the hub may be used to prevent fluid from leaking outof the cannula insertion site in the skin in the follower manner. Thehub of the infiltration cannula serves as a connector. The distal end ofthe hub attaches to the cannula, while the proximal end of the hubdetachably connects to the plastic tube set which carries tumescentsolution to the cannula. With a slight modification, the hub can alsoassist in reducing or virtually eliminating leakage of tumescent fluidout through the skin incision or adit site. An adit is a small roundhole in the skin typically produced by a biosy punch. The hub 20 mayhave a conical configuration. The hub 20 may become narrower from theproximal end of the hub to the distal end of the hub. The rate at whichthe hub 20 becomes narrow may be less than about fifteen degrees withrespect to a centerline of the hub. The outer surface of the hub 20 mayhave a plurality of rounded circular ridges equally spaced apart. Theadit may be formed so as to have a diameter which is less than adiameter of the cannula or the outer surface of the hub. To minimizeleakage of tumescent fluid out onto the surface of the skin, the cannulamay initially be inserted into the adit. The adit is slightly stretchedto accommodate the cannula. The cannula may be fully inserted into thesubcutaneous tissue of the patient such that the distal end of the hubcontacts the adit. The hub may then be pushed into the adit such thatthe inner diameter of the adit expands and slides over the roundedcircular ridges formed on the distal end of the hub. The hub is gentlywedged into the adit until there is a snug fit between the infiltrationcannula and the adit. Leakage of fluid out of the adit may also beminimized by placing the proximal most aperture on the cannulasufficiently deep within the subcutaneous tissue such that fluidinjected from the most proximal hole produces localized interstitialtumescence and a snug fit of the tissue against the cannula. It is alsocontemplated that the hub have other shapes such as curved, linear,parabolic, or combinations thereof.

Flexible plastic infiltration cannulas 30, such as the one shown inFIGS. 3, 4 and 6 are single use cannulas and can be used in one ofseveral unique ways. First, an anesthesiologist, surgeon, untrainedfirst responder, or even a victim can insert infiltration cannula 30with stylet 46 into the subcutaneous tissue 50, remove the stylet 46,then attach an IV tubing to the infiltrator and inject tumescent localanesthesia or other tumescent fluid into the targeted area withoutsubsequent repositioning of the infiltration cannula 30. The plasticflexible nature of the tubular needle 32 of the disposable plasticcannula 30 allows the patient to move or change position of the bodywithout risk of injury that might result if a patient moves while arigid steel cannula is inserted.

Preferably, the stylet 46 is formed of a rigid material such as metal,stainless steel, or plastic material. The stylet 46 should besufficiently rigid so as to guide the tubular needle 32 of the cannula30 into the subcutaneous tissue 50. The stylet 46 may be solid (see FIG.4) or hollow (see FIG. 7) through its center. The plastic cannula 30 canbe blunt-tipped with the metal stylet tip 48 covered by the rounded tip39 of the plastic cannula 30, as shown in FIG. 4. Alternatively, theplastic cannula 30 can be open-ended with the stylet 46 extending ashort distance past the end 39 of the plastic cannula 30 as shown inFIG. 6. In the case of the open ended cannula, the stylet 46 can beeither blunt-tipped (see FIG. 6; requiring a skin incision to permitinsertion into the subcutaneous space), or sharp-tipped (see FIG. 7;permitting the cannula to be inserted directly through the skin and intothe subcutaneous space or muscle without requiring a preparatory skinincision). The sharp-tipped stylet 46 can be formed in either a solid(see FIG. 4) or hollow (see FIG. 7) cross-sectional configuration. Theutility of a sharp tipped hollow stylet is that it can be inserteddirectly through the skin and then advanced painlessly through thesubcutaneous tissue by slowly injecting local anesthetic solutionthrough the stylet as it is slowly advanced, thereby anesthetizing thetissue in advance of the stylet's tip.

If the stylet 46 is hollow through its center 58, then apertures 54 maybe formed along an entire length or along a portion (e.g., about 33% to100%) of the length of the tubular needle 56 of the stylet 46, as shownin FIG. 7. The hollow stylet 46 (see FIG. 7) may be utilized in asimilar fashion as the cannula 10 shown in FIGS. 1 and 2 and describedherein. By way of example and not limitation, during use, the tubularneedle 56 shown in FIG. 7 may be inserted into the cannula 30. Thecombined tubular needle 56 and cannula 30 may be inserted through thesubcutaneous tissue 50 of the patient. The tubular needle 56 may beremoved from the patient and the cannula 30. The tubular needle 56 ofthe stylet 46 may now be reinserted into the patient at a different siteand used as a rigid cannula similar to the cannula 10 discussed inrelation to FIGS. 1 and 2.

The stylet 46 shown in FIG. 7 has apertures 54 about the periperhy oftubular needle 56 of the stylet 46. The apertures 54 may have a patternwhich is dissimilar to the pattern of apertures 38 formed in the tubularneedle 32 of the cannula 30. Alternatively, the apertures 54 may have apattern which is identical to the pattern of apertures 38 formed in thetubular needle 32 of the cannula 30. As a further alternative, some ofthe apertures 54 may have a pattern which is identical to the pattern ofapertures 38 formed in the tubular needle 32 of the cannula 30. Also,some of the apertures 54 may have a pattern which is dissimilar to thepattern of apertures 38 formed in the tubular needle 32 of the cannula30. During use, the medical professional may insert the stylet 46 (seeFIG. 7) with apertures 54 into the cannula 30. The apertures 54 of thestylet 46 may be aligned or misaligned to the apertures 38 of thetubular needle by turning the stylet 46 within the cannula 30. Thestylet 46 may have a hub with a similar configuration as hub 40. The hubof the stylet 46 may also be wedged into the adit of the patient tominimize or eliminate leakage of fluid, as discussed herein.

The plastic cannula shown in FIGS. 3 and 4 is similar to an IV catheterexcept the sharp hollow stylet used for the insertion of an IV cathetercan be replaced by a solid obturator/stylet 46 that can be either sharpor blunt tipped. Except for the removable stylet 46, the plastic cannula30 is similar to the stainless steel cannula 10 shown in FIGS. 1 and 2and described above. The plastic cannula 30 includes a flexible tubularneedle 32 having a proximal end 34 and a distal end 36. The distal endhas apertures 38 and the proximal end 34 may be devoid of apertures. Asstated above, in exemplary embodiments, the pattern of apertures 38 inthe cannula 30 are distributed over the distal 33% to 100% (see FIG. 4)of the tubular needle 32 of the cannula 30. For example, if the tubularneedle 32 of cannula 30 shown in FIGS. 3 and 4 has a length D of 15 cmand the pattern of apertures are distributed over a length d1 of 13.5cm, then the apertures 38 are distributed over 90% of the cannula. As afurther example, if the tubular needle 32 of cannula 30 shown in FIGS. 3and 4 has a length D of 15 cm and the pattern of apertures aredistributed over a length d1 of 15 cm, then the apertures 38 aredistributed over 100% of the cannula. To stop leakage of tumescent fluidout of the adit site, the hub may be wedged into the adit site, asdiscussed above.

A typical infiltration cannula 10, 30 may have a diameter equivalent to20, 18, 16 or 14 gauge with small apertures 18, 38 placed every 5 mmalong the cannula in a spiral or helical pattern. The infiltrationcannula 10, 30 may be 20-14 cm in length. A typical infiltration cannula10, 30 is 15 cm or 20 cm in length. It will be appreciated that thedimensions used herein are exemplary and that the cannula dimensions,range of gauge, length range of cannula, relative size shape and patternof apertures can vary greatly depending upon clinical preference.

The proximal end 34 of the tubular needle 32 shown in FIGS. 3 and 4 isattached to a hub 40 that is used by the anesthesiologist or surgeon tohold the cannula 30 during the infiltration procedure. The hub 40 isconnected to the tubular needle 32 at a first end 42 and has a connector44 at an opposing second end. The connector 44 is connected to a fluidsource. As described above and shown in FIG. 4, the stylet 46 can beinserted and removed from the cannula 30.

Infiltration using a plastic infiltration cannula 30, such as the oneshown in FIGS. 3 and 4, can be accomplished using an infiltration pump.Alternatively, the force of gravity could be used to push the tumescentfluid into the tissues by hanging a reservoir plastic bag of tumescentlocal anesthesia (or other dilute drug, such as a chemotherapeutic agentor antibiotics) on an IV pole and connecting bag to the infiltrationcannula by an IV line.

Another application is the injection of tumescent local anesthesia intoa localized area through which a surgeon plans to make a surgicalincision. The effects of vasoconstriction, resulting from theepinephrine in the tumescent local anesthetic solution, within thetumesced tissue minimizes surgical bleeding. In a uniquely preemptivefashion, the present invention can produce, via the pre-operativeinfiltration of tumescent local anesthesia, prolonged post operativeanalgesia and also preemptively reduce the risk of surgical woundinfections resulting from the bacteriacidal effects of lidocaine.

Lidocaine is bactericidal in vitro against S. aureus, and this effectincreases with greater duration of exposure. In a dose-dependentfashion, clinical doses of lidocaine have been shown to inhibit thegrowth of bacterial pathogens commonly encountered in nosocomial woundinfections. A tumescent epinephrine induces profound localvasoconstriction resulting in significantly delayed systemic absorptionof a tumescent antimicrobial drug from subcutaneous tissue. Incommercially available concentrations, the systemic absorption of anaqueous solution of lidocaine requires approximately 2 to 4 hours. Incontrast, the systemic absorption of tumescent lidocaine requires 24hours or more. Accordingly, a tumescent antibiotic can be expected toremain within the peri-incisional tissue at least 12 times longer than aroutine aqueous antibiotic solution and the action would be far moreeffective. Moreover, a tiny hematoma within an incision may be anisolated avascular space and a potential nidus for an infection. Theprofound and prolonged vasoconstriction induced by tumescent epinephrineminimizes surgical bleeding and hematoma formation and therefore reducesthe risk of SSI. Hypothermia is a major risk factor for postoperativeSSI. Mild perioperative hypothermia, is common among patients havingsurgery under general anesthesia. The incidence of SSI was 5.8% in thenormothermic (core body temperature 37 degrees C.) group and 18.8% inthe hypothermic group (34.4 degrees C.) in a randomized, double blindtrial. (Kurtz A, Sessler D I, Lenhardt R. Perioperative normothermia toreduce the incidence of surgical-wound infections and shortenhospitalization. Study of wound infection and temperature group. N Eng JMed 334:1209-15, 1996). Hypothermia also causes delays in moving thepatient out of the recovery room. With surgery totally by tumescentlocal anesthesia there is no evidence of post operative hypothermia.

Infiltration of a tumescent solution containing lidocaine, epinephrine,and an antibiotic is likely to provide significantly improved SSIprophylaxis. Tumescent infiltration of antibiotics into peri-incisionalskin and subcutaneous tissue offers the following advantages: prolongedlocal tissue concentrations of antibiotics, prolonged systemic deliveryof antibiotic to tissues distant from the incision site, andsignificantly, the systemic absorption of tumescent lidocaine mimics IVdelivery of lidocaine which is known to reduce postoperative pain andhasten post operative discharge from the hospital. The infiltrationcannula discussed herein is the optimal device for tumescent delivery ofantimicrobial drugs.

Yet another application is to provide an easily accessible route forsystemic administration of crystalloid fluids/electrolytes for systemichydration or for other types of drug therapy. Potential clinicalapplications include emergency resuscitation with systemic fluids insituations where insertion of an IV catheter into a vein cannot bereadily achieved. Examples of situations where emergency access forintravenous delivery of fluids might not be possible include acutetrauma or burn wound in civilian or military situations and very obesepatients in which finding an accessible vein for IV access can bedifficult even for a physician skilled in performing “IV cut-down”procedures. The infiltration cannula discussed herein may be a valuableadjunct to fluid resuscitation in an ambulance or an emergency room.Another application may be the emergency treatment of dehydrationassociated with pandemic influenza, prolonged vomiting or diarrhea as aresult of chemical warfare or biological warfare (e.g., epidemic choleraamong pediatric patients in rural third world settings) or other typesof medical emergencies which overwhelm a medical center's capacity tocare for incoming victims. A subcutaneous infiltration catheter caneasily be introduced by a layman, whereas inserting an IV catheter intoa vein of a patient that is severely dehydrated can be difficult evenfor a skilled physician. Delivery of systemic fluids by subcutaneousinfiltration is safer than an IV infusion in a zero gravity situation(for example, the Space Station). The addition of a small amount ofcapillary vasodilator (e.g., methylnicotinamide) to the subcutaneousfluid can be used to accelerate the systemic absorption of the fluid ordrug into the intravascular space. Further applicational uses for thepresent invention are described in co-pending application Ser. No.10/877,337, filed Jun. 25, 2004, the disclosure of which is expresslyincorporated herein by reference.

The continous systemic drug delivery by tumescence has a similartherapeutic effect to continuous IV infusion but without the inherentexpense, difficulties, and risk of an IV infusion. Compared to eitheroral delivery of a drug (inconsistent absorption from thegastrointestimal tract), or periodic intramuscular (IM) injections of adrug (variable serum concentrations), continuous systemic delivery ispreferred in order to achieve prolonged and relatively uniform bloodconcentrations of the drug. This is especially true in critically illpatients. Tumescent delivery of a drug, placed in a tumescent solutioncontaining epinephrine as a vasoconstrictor, produces a prolongedcontinuous system absorption of the drug over an interval of more than24 hours. The simplicity and inexpensive equipment required to achievecontinuous tumescent systemic drug delivery is clearly an advantageamong medically impoverished populations, and in the demandingconditions of battlefield or at the scene of a mass casualty.

Yet another application is related to astronauts and systemic deliveryof medication. In particular, the therapeutic options for treating aninjured astronaut are limited. The fate of injured airplane pilots,passengers and astronauts are similar in that we presently havevirtually no in-flight capability for treating an acute traumaticinjury. If a pilot or astronaut survives the immediate effects of anexplosion, burn, or decompression injury, or if there is an acutenon-traumatic medical illness, it is assumed that the victim must returnto terra firma for any significant therapeutic intervention such asproviding systemic fluid replacement. The tumescent infiltrator iscapable of providing systemic fluid and thus it is successfully solvinga problem that has either never before been recognized, or has neverbefore been solved by a simple device and technique.

The present invention allows improved emergency medical care for aninjured astronaut on-board the ISS. Repeated and prolonged extravehicular activities (EVA) expose astronauts to greater risk of physicaltrauma injury. Potential injury to astronauts include decompressioninjury-induced neurological injury and coma, acute pneumothorax, burns,and radiation injury. Assembly and maintenance of the ISS requires anunprecedented number of spacewalks, which expose astronauts to the riskof decompression sickness (DCS). In addition to humanitarian concerns,there is a strong economic incentive to provide on-board care for acuteillness or trauma: the only alternative would be to abort an expensivemission and immediately return the victim to earth.

At present, there is no safe and easy means of providing the equivalentof IV fluids to a patient in space. Assuming there is a fellow astronautwith the requisite clinical skill to insert an intravenous (IV) catheterin a weightless environment, there is a problem of zero gravity. Whereasgravity separates air and water into distinct layers, in zero gravitythere is a risk of air bubbles from the IV bag entering the IV line andcausing intravascular air embolism. Because subcutaneous air isrelatively safe, the tumescent infiltration cannula, by allowingeffective systemic fluid resuscitation via subcutaneous infiltration,overcomes the above problems, and allows a person without clinicalskills to safely provide the equivalent of IV fluids.

The cannula 10, 30 is intended to be inserted far enough through theskin 52 so that all of the apertures 18, 38 are within the fat 50 ormuscle of the patient. If the apertures 18, 38 are distributed overabout 100% of the cannula, the hub may be wedged into the adit toprevent or minimize leakage of the tumescent fluid out of the adit. Oncethe cannula 10, 30 is properly positioned, it can remain stationarywhile the local anesthetic (or other pharmaceutical) solution isinjected. Since the cannula remains stationary, the associated pain ordiscomfort typically caused by the reciprocating in and out movement ofprior art cannulas is reduced or eliminated. Accordingly, the cannula ofthe present invention permits infiltration of multi liter volumes oftumescent fluid into the patient in a safe and painless manner.

After one portion of the targeted area has been tumesced, theinfiltration is briefly terminated (either by turning off the pump or byclamping the IV tubing) while the cannula 10, 30 is repositioned intoanother area of the subcutaneous tissue. Typically, the cannula isrepositioned at the rate of about once per minute. The infiltration isthen restarted with the cannula stationary in its new position. Sincethe apertures are distributed over the distal 33% to 100% of thecannula, the apertures distribute tumescent fluid into the patient alongthe entire length of cannula insertion. The cannula does not have to bereciprocated in and out to infiltrate the subcutaneous tissue like priorart cannula. Progressing repeatedly in this fashion, eventually all thefat within a targeted area becomes tumescent and profoundly anesthetic.As such, such method can obviate the need for general anesthesia orheavy IV sedation in most surgical procedures restricted to the skin andsubcutaneous tissue.

The infiltrator 10, 30 can also be used in the traditional mode wherebythe cannula 10, 30 is moved through the targeted tissue while the fluidis simultaneously pumped through the cannula 10, 30 and into thesubcutaneous tissue 50.

Another unique aspect of the tumescent technique's reservoir effect isthat one can conveniently achieve a long, slow, steady absorption of adrug delivered to the subcutaneous space 50 using periodic injections ofa tumescent solution. In certain situations, using a slow IV infusion,the alternative technique, can achieve a slow systemic absorption of adrug but may be difficult, require greater clinical expertise, be moreexpensive, and therefore, less practical than the technique describedherein.

FIG. 5 is a flow diagram illustrating steps performed in an exemplaryinfiltration procedure using a cannula 10, 30 such as the one shown inFIGS. 1 and 2 or the one shown in FIGS. 3 and 4, respectively. Theprocedure begins by inserting the tubular needle 12, 32 of theinfiltration cannula 10, 30 into a desired subcutaneous tissue site 50,e.g., via an incision in the patient's skin 52 (block 100). Fluid isthen transported from the fluid source (e.g., an IV bag) into thecannula 10, 30 via the connector 24, 44 that is connected to the fluidsource. The fluid is transported from the connector 24, 44 through thehub 20, 40 and into the tubular needle 12, 32 (block 102). The fluid isthen ejected from the cannula 10, 30 into the subcutaneous tissue 50 ofthe patient via the apertures 18, 38 at the distal end 16, 36 of thetubular needle 12, 34 of the cannula 10, 30 (block 104).

The fluid is transported (block 102) and ejected (block 104) untilinfiltration at the current site is completed (yes in decision block106). Complete infiltration at the current site may take approximatelyone or two minutes. The fluid can be injected into multiple sites inorder to distribute the solution over a greater area.

Infiltration at a particular site may be deemed complete upon emptyingof the fluid source or based on the anesthesiologist or surgeon'sdecision to stop the infiltration at the current site. After one portionof the targeted area has been tumesced, the infiltration can be brieflyterminated (either by turning off the pump or by clamping the IV tubing)while the cannula 10, 30 is repositioned into another area of thesubcutaneous tissue. The infiltration may then be restarted with thecannula stationary in its new position. If the infiltration at a site iscomplete (yes in decision block 106), the cannula is removed from thecurrent site (block 108). If the infiltration at the current site is notcomplete (no in decision block 106), fluid is transported from the fluidsource (block 102) and ejected into the subcutaneous tissue (block 104)until infiltration at the site is complete (yes in decision block 106).

If infiltration is complete at the current site (yes in decision block106) but infiltration is not complete (no in decision block 110), thetubular needle 12, 32 of the infiltration cannula 10, 30 is insertedinto a new area of subcutaneous tissue 50. By way of example and notlimitation, the tubular needle 12, 32 may be inserted into a new areaadjacent the current site. The adjacent site may be partiallyanesthetized by infiltration of the anesthetic solution at the currentsite. As such, pain to the patient caused by insertion of the tubularneedle 12, 32 is minimized, eliminated or greatly reduced. The processdescribed above is performed until the infiltration process is complete(yes in decision block 110). This process can be continuous or repeatedintermittently. It is contemplated that infiltration of up to about 50%of the patient's body may be achieved in the manner described herein.

As described above, multiple infiltration cannulas (e.g., can be used atonce). Thus, a second or additional cannulas can be inserted (block 100)at the same time as a first cannula is being removed (block 108). Forexample, the second cannula may be inserted parallel to the firstcannala and into an area immediately adjacent to the area in which thefirst cannula is inserted. In this manner, the pain usually associatedwith the insertion of the cannula into the patient's fat tissue isreduced or eliminated because the first cannula has already at leastpartially anesthetized the area in which the second cannula is inserted.The second cannula is positioned adjacent the first cannulaapproximately every one or two minutes. The first cannula may then beremoved from the patient's body after the second cannula is inserted.Moreover, the infiltration process need not be interrupted in order toreposition a single cannula. Progressing repeatedly in this fashion,eventually all the fat within a targeted area becomes tumescent andprofoundly anesthetic. As such, such method can obviate the need forgeneral anesthesia or heavy IV sedation.

The plastic infiltration cannula shown in FIGS. 3 and 4 may be used byeither a lay person or a clinical professional for the delivery oftumescent fluid for either tumescent local anesthesia, tumescentantimicrobial therapy, or emergency delivery of systemic fluids bytumescent infiltration. In an aspect of the cannulas 10, 30, it iscontemplated that such cannulas 10, 30 may be utilized for continuoussystemic tumescent delivery of a drug which produces a continous systemabsorption of the drug over nearly 24 hours in a fashion similar to acontinuous IV infusion.

The infiltration cannula 10, 30 discussed herein is a subcutaneousdevice and not an intravascular device for infiltration of multi-litervolumes of fluid into areas of up to 50% of the total body surface area.For example, the infiltration cannulas 10, 30 infiltrates approximately1,000 times the volume of fluid delivered by the Schwartz devicediscussed in the background.

Additional modifications and improvements of the present invention mayalso be apparent to those of ordinary skill in the art. Thus, theparticular combination of parts described and illustrated herein isintended to represent only a certain embodiment of the presentinvention, and is not intended to serve as a limitation of alternativedevices within the spirit and scope of the invention.

What is claimed is:
 1. An infiltration cannula insertable into an aditof a patient for infiltrating fluid into the patient, the infiltrationcannula comprising: a tubular needle defining a proximal end, the needlecomprising a plurality of apertures disposed in a pattern between about33% to about 100% of the distal end portion, the apertures configured toinfiltrate fluid into subcutaneous tissue or muscle of a patient; and ahub configured to be held by a person infiltrating the fluid into thepatient, the hub having a first end and an opposing second end, the hubflaring outwardly from the first end to the opposing second end, thefirst end being attached to the proximal end of the tubular needle, thesecond end comprising a connector configured to connect to an inputsource for receiving the fluid to be infiltrated into the subcutaneoustissue of the patient, the fluid flowing from the connector, through thehub, into the cannula, through the plurality of apertures and into thepatient; wherein the outward flared portion of the hub is wedgeable intothe adit to minimize leakage of the fluid flowing out of the proximalapertures and out of the adit.
 2. The infiltration cannula of claim 1wherein the hub from the first end to the opposing second end has aconical shape.
 3. The infiltration cannula of claim 1, wherein thedistal end of the cannula is closed.
 4. The infiltration cannula ofclaim 1, wherein the distal end of the cannula is open with a holeallowing a tip of a rigid stylet to protrude through.
 5. Theinfiltration cannula of claim 1, wherein the apertures are round oroval.
 6. The infiltration cannula of claim 1 wherein the tubular needleis flexible or rigid.
 7. The infiltration cannula of claim 1 furthercomprising a solid stylet for guiding the tubular needle intosubcutaneous tissue or muscle of the patient.
 8. A method ofinfiltrating fluid into subcutaneous tissue or muscle of a patient, themethod comprising: a) providing a first cannula having a tubular needlewith apertures disposed about a distal 33% to 100% end of the needle; b)inserting the tubular needle into an adit of the patient; c) insertingall of the apertures disposed on the needle into the patient; d) wedgingan outwardly flaring hub into the adit for forming a seal between thehub and an inner periphery of the adit to minimize leakage of fluid tobe flowed through apertures of the first cannula; e) flowing fluidthrough the hub, apertures and into the subcutaneous tissue of thepatient; f) blocking fluid flow out of the adit between the needle andthe skin of the patient due to flow of fluid through proximal aperturesdisposed on the needle.
 9. The method of claim 8 further comprisingrepeating steps of a)-f) with a second cannula by inserting the secondcannula into the patient adjacent to the first cannula.
 10. The methodof claim 9 further comprising the step of removing the first cannulaafter performing steps a)-f) with the second cannula.
 11. The method ofclaim 9 wherein the steps a)-f) are performed with the second cannulaafter performing step e) with the first cannula for about one and a halfminute.
 12. The method of claim 8 further comprising the steps ofstopping fluid flow through the hub and apertures of the first cannula;removing the first cannula; inserting the first cannula into a secondsite; and repeating steps a)-f) while the first cannula is disposed atthe second site.
 13. A method of minimizing infections at a surgicalsite, the method comprising the steps of: providing a solutioncontaining an antibiotic and a vasoconstrictive drug; inserting atubular needle having apertures into an adit of the patient such thatthe tubular needle is adjacent the surgical site to infiltrate thesolution at the surgical site; flowing the antibiotic/vasoconstrictivedrug solution through the tubular needle and out of the apertures toconstrict the blood vessels and delay systemic absorption of theantibiotic for prolonging a length of time that the antibiotic remainsat the surgical site; and performing surgery at the surgical site. 14.The method of claim 13 further comprising the step of mixing lidocaineinto the antibiotic/vasoconstrictive drug solution for providing anantibacterial effect.
 15. The method of claim 13 wherein the performingsurgery step occurs after the flowing step.
 16. A method of hydrating adehydrated patient, the method comprising the steps of: providing ahydrating solution in a container; inserting a flexible tubular needleconnected to the container of hydrating solution into the patient;flowing the hydrating solution through the flexible tubular needle, outof apertures disposed on the flexible tubular needle and into thepatient for hydrating the dehydrated patient.
 17. The method of claim 16wherein the inserting step is performed by a person untrained inestablishing intravenous access.
 18. The method of claim 16 wherein theinserting step is performed by inserting the flexible tubular needleinto the subcutaneous tissue of a thigh of a person.
 19. An infiltrationcannula insertable into an adit of a patient for infiltrating fluid intothe patient, the infiltration cannula comprising: a flexible tubularneedle defining a hollow center, the needle comprising a plurality ofneedle apertures disposed in a pattern between about 33% to about 100%of the distal end portion, the needle apertures configured to infiltratefluid into subcutaneous tissue or muscle of a patient; and a rigidstylet having a plurality of stylet apertures disposed in a patternbetween about 33% to about 100% of the distal end portion, the styletapertures configured to infiltrate fluid into subcutaneous tissue ormuscle of a patient, the stylet being sized and configured to beremoveably insertable within the hollow center of the tubular needle.20. The infiltration cannula of claim 19 wherein the pattern of theneedle apertures is identical to the pattern of the stylet apertures.21. The infiltration cannula of claim 19 wherein the pattern of theneedle apertures is dissimilar to the pattern of the stylet apertures.22. The infiltration cannula of claim 19 wherein the stylet is sized andconfigured to the hollow center of the tubular needle such that thestylet is rotateable within the tubular needle to align or misalign thepatterns of needle apertures and stylet apertures.
 23. The infiltrationcannula of claim 19 wherein the stylet has a blunt tip or a sharp tip.